There are 16 different shades of gray seamless paper. Although many of them can look similar, each one does offer a slightly different look and feel.
Below are some side-by-side comparisons to help with selecting which shade is best for you. Remember though, lighting can play a large part in how your backdrop photographs. The same backdrop can look very different depending on the number of lights, type of lights and the position of the lights.
If you're having trouble deciding which color is best for you, you may also consider purchasing a Seamless Paper Chip Chart.